Hi
Please have a look at this article, this seems like your problem too.
Link:- http://blogs.adobe.com/dmcmahon/2012/03/12/cq5-preview-mode-in-sidekick-does-not-refresh-automatically/
//preview mode in sidekick does not refresh automatically
The solution is simply to force a page refresh automatically when switching to preview mode.
- Open /libs/wcm/core/components/init/init.jsp
- Add the previewReload property as follows and save the changes:
CQ.WCM.launchSidekick("<%= currentPage.getPath() %>", { propsDialog: "<%= dlgPath == null ? "" : dlgPath %>", locked: <%= currentPage.isLocked() %>,previewReload: "true"}); - Now CQ is setup to refresh automatically when switching to preview mode.
Workaround :- https://helpx.adobe.com/experience-manager/kb/LinkToPreviewMode.html
Please check the browser console errors and error.log to better debug this problem.
Thanks and Regards
Kautuk Sahni